1. Field of the Invention
The invention relates to electrical feed-throughs, suitable in particular for high currents, and to use thereof. With such a feed-through, electric currents can be introduced into and removed from safety-related enclosures and in this way electrical loads can be supplied with electric current. Also comprised in particular are feed-throughs in the low voltage range and medium voltage range. They are generically referred to generally as large feed-throughs, since their components can have diameters ranging from a few centimeters to many centimeters and the total weight may be several kilograms.
2. Background
In the case of enclosures for storing or transporting flammable hazardous material, enclosures of energy generating or storing devices or enclosures in which hazardous substances occur and/or are stored, known collectively as safety enclosures, it is often necessary to introduce and/or remove electric currents into and/or from the enclosure. For example, submersible pumps, in particular also cryogenic pumps, are used in installations for conducting and/or transporting liquefied natural gas, arranged within the enclosure. In order to introduce the power required for the pumps into the interior of the enclosure, connection devices with sealing electrical feed-throughs are used. In the case of energy generating units, for example steam generators of power plants, the energy generated must be safely removed and/or apparatuses in these energy generating units have to be supplied with current. For this purpose, a feed-through is typically flange-mounted on a flange of the safety enclosure, for example a pressure vessel, in particular a liquefied gas tank.
In particular in the case of pressure vessels of flammable gases and/or liquids, it is important here that the feed-through remains sealed over a long time. Especially when storing flammable substances, which can form explosive gas mixtures, there is still the risk here that, even in the event of extremely small leakages that are not in themselves critical, gas mixtures may be formed in closed-off regions of the feed-through. For example, such regions may be formed in mounted protective housings. If a deflagration then occurs, the feed-through may be damaged in such a way that unsafe material quickly escapes from the enclosure that is to be closed off. This is also relevant in particular in the case of installations for generating nuclear energy, in particular in order to ensure secure containment of the reactor housing and/or sealing of the reactor housing itself even in the event of a fault.
EP 2 031 288 B1 describes an electrical feed-through for liquefied gas tanks in which an electrical conductor is soldered in a flange by means of an insulating bushing. The flange has a through-opening, in which the electrically insulating bushing is connected to the flange with the help of the connecting elements with the numbers 20 and 22 as used in the drawings. The insulating bushing is tubular and has inside an electrical conductor of a smaller diameter than the inside diameter of the bushing. At its ends, the gap between the bushing and the conductor is hermetically sealed, so that there is a relatively great clearance between the bushing and the conductor. In the bushing there is a bore. The flange is of a two-part design, so that between the flanges there is a clearance, which connects the clearance in the bushing to the clearance between the flanges through the bore in the bushing, or a one-part flange is provided with a bore that corresponds to the bore of the bushing. By monitoring the pressure in the clearance of the bushing, gas penetrating into the bushing can be detected, and consequently damage to the feed-through can be monitored.
This feed-through has the problem that the electrically insulating bushing is of a certain length and protrudes beyond the surface of the flange. It is tubular and has a clearance that extends around the inner conductor. The material of the bushing is a ceramic, which is known as being a brittle material. In the case of such a feed-through unit, specifically the bushing may rupture under mechanical loading, especially since it protrudes beyond the surface of the flange. In the event of rupture, the barrier between the safety enclosure and the surroundings would be breached. Apart from that, the material of the bushing and of the inner conductor must be made to match one another with respect to their thermal expansion. Furthermore, the production of such a bushing involves considerable manufacturing expenditure.
DE 10 2013 202 614 A, not yet published at the time of the first application of the present invention, describes a feed-through in a flange in the case of which the functional element, for example a conductor for electric current, is glazed-in in a flange, the insulation components of glass not protruding beyond the surface of the flange. In order to provide electrical conductors for high current intensities with the aid of this feed-through, it is provided in this document that an electrical conductor is held by a first functional component, which in turn is glazed-in in the through-opening. The electrical conductor consists in particular of copper. Since this cannot be glazed in directly, the copper conductor is connected to the first functional component without a gap. The first functional component consists of a material that can be glazed in. Usually, the electrical conductor is in this case formed by a copper rod which is surrounded by a steel tube that establishes the connection with the glass material of the insulation component. In this case, the sealing of the connection of the copper rod to the steel tube must be ensured. Such a solution is mechanically stable, but requires increased production expenditure, in particular on account of the required connection of the copper rod and the steel tube.